1. Field of the Invention
The present invention generally relates to image display systems which process image data in the form of rows and columns of pixel data and, in particular, to such systems which process such pixel data for the purpose of modifying any of a variety of the display aspects thereof.
2. Statement of the Prior Art
Image display systems used for processing and displaying images derived from digital data are well known and have taken a variety of forms. Generally, these forms may be divided into those systems which use digital processing exclusively and those systems which use combinations of digital and analog processing.
In the area of digital processing, data is typically handled on either a pixel by pixel basis or a vector basis. The vector approach is a shorthand form of notation which allows groups of pixels to be defined by a predetermined number of digital characters independently of the number of pixels being defined. This method is typified by U.S. Pat. Nos. 3,925,776 and 3,944,997. In general, the vector method is noted for economy due to the limited amount of data necessary to define a display. This makes such systems particularly adaptable to installations requiring the long-distance transmission of image data where the accuracy of very large blocks of data is at risk. A related benefit is the reduction of the access time for such information, thus increasing the efficiency for a given data base by practically supporting multiple users. Unfortunately, the vector method is essentially limited in the amount of detail which may be displayed and thus is not suitable for high resolution applications.
Situations requiring greater detail usually process and display data in the form of individual pixels with each pixel having an intensity or brightness level associated therewith. Due to the large amount of data which must be handled by such pixel systems, they are generally cumbersome and inefficient to use. The inefficiency is related directly to data handling as the accessing and processing times required are proportional to the numbers of pixels used, and usually impact both the operators time of an individual user and the practicality of a multiple user system. This problem is further inflamed by high resolution requirements which increase the number of pixels per image.
The other form of image processing generally includes a combination of analog and digital processing. This method tends to be inflexible and costly inasmuch as analog circuits are not conveniently variable and one or more analog/digital conversions of the data are required. The limited variability of analog circuits typically requires that hard-wired circuitry be changed to affect any significant display parameter or hardware changes. Further costliness is incurred in high resolution displays which require high speed processing circuitry to supply the processed image signal. The displayed image presented is also limited in that the entire display must be treated and processed as a whole. Generally, it is not possible to independently do different manipulations or different portions of the displayed image.
For these reasons, needs arise in areas requiring the display of exceptional detail, such as medical imaging, for a pixel handling system which is flexible and practical to use. Some achievements have been recently made which provide for high speed processing of pixel data and thereby enable development of a practical, time efficient system. One example is the area of instant imaging cat-scanning which processes the sampled digital data from a cat-scanner during the scanning process to provide a completed image very shortly after the completion of scanning. An example of such a system is described in U.S. Pat. No. 4,135,247. Unfortunately, such systems are limited in the flexibility with which the image data produced can be handled.